All three phase terminals U, V, and W are connected in the positive direction to the positive pole of the motor vehicle battery via the diodes and to ground with one diode in the reverse direction. Electronic regulators used to regulate the output voltage of three-phase generators require information about whether the generator is operating and, if so, at which rotational speed. This rotational speed information is obtained by observing one or more phase terminals of the generator.
German Published Patent Application No. 43 08 769 relates to a method for monitoring and protecting high-current diodes. In the method known from German Published Patent Application No. 43 08 769, which is used in welding systems in particular, the high-current diodes are monitored by determining the temperature of the diodes by simulating the temperature of the diodes electrically by an analog method, preferably via an RC network. A comparison with a reference signal corresponding to a maximum allowed temperature of the high-current diodes is performed. First, the current flowing through the high-current diodes is detected, and then a current corresponding to the measured value is applied to a measuring line. A voltage is generated, allowing the thermal response of the high-current diode to be visualized by using an RC network. The simulated voltage is ascertained using a preselectable reference voltage; in the case when the simulated voltage exceeds the preselectable reference voltage, an error signal is generated. A system for implementing the method includes an ammeter that measures the current flowing across the high-current diode and maps a measuring signal. Furthermore, the arrangement includes a controlled current source which applies a current corresponding to the measuring signal delivered by the ammeter to a measuring line and an RC network block, which applies a voltage simulating the thermal response of the high-current diode to the measuring line. Finally, a monitoring circuit is provided and delivers a signal when the voltage applied to the measuring line exceeds a preselectable reference value.
A rectifier is known from German Published Patent Application No. 100 05 183. This rectifier includes semiconductor rectifier elements for rectifying an alternating electric quantity applied to an input u, v, w of the rectifier and an output for picking up the rectified electrical quantity. A fusible cutout is connected between the rectifier elements and the output, the fusible cutout having a semiconductor chip made of the same semiconductor material as the rectifier elements. The semiconductor rectifier elements have rectifier semiconductor chips surrounded by a housing, the semiconductor chip of the fusible cutout being surrounded by a housing having essentially the same design as the housing of the semiconductor rectifier elements.
If one of the diodes of a three-phase generator is defective, whether due to a short-circuit or an interruption, the generator is able to supply only a reduced output current, so an unacceptably high voltage dip may occur when a major electric load is connected to the vehicle electrical system. Electronic regulators are usually used to regulate the output voltage of a three-phase generator and require information about whether the generator is in operation and, if so, at what speed. This rotational speed information is made available by observing one or more of the phase terminals of the three-phase generator. The frequency of the alternating voltage is directly proportional to the rotational speed of the three-phase generator.
All these methods and/or arrangements and devices usually have the disadvantage that the diode faults mentioned above, i.e., a short circuit and/or an interruption, is/are typically either not detected at all or are not detected adequately. Furthermore, according to the approaches outlined above, the design complexity for implementing this design in the regulator or for accommodating the sensors is usually substantial, thus greatly increasing the manufacturing cost.